LPC1547JBD48 datasheet(41/99 Pages) NXP

41 / 99 page

LPC15XX

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Product data sheet

Rev. 1 — 19 February 2014

41 of 99

NXP Semiconductors

LPC15xx

32-bit ARM Cortex-M3 microcontroller

8.26.1 Features

• Seven selectable inputs. Fully configurable on either the positive side or the negative

input channel.

• 32-stage voltage ladder internal reference for selectable voltages on each

comparator; configurable on either positive or negative comparator input.

• Voltage ladder source voltage is selectable from an external pin or the 3.3 V analog

voltage supply.

• 0.9 V internal band gap reference voltage selectable as either positive or negative

input on each comparator.

• Temperature sensor voltage selectable as either positive or negative input on each

comparator.

• Voltage ladder can be separately powered down for applications only requiring the

comparator function.

• Individual comparator outputs can be connected internally to the SCT and ADC trigger

inputs or the external pins.

• Separate interrupt for each comparator.

• Pin filter included on each comparator output.

• Three propagation delay values are programmable to optimize between speed and

power consumption.

• Relaxation oscillator circuitry output for a 555 style timer operation using comparator

blocks 0 and 1.

8.27 Temperature sensor

The temperature sensor transducer uses an intrinsic pn-junction diode reference and

outputs a CTAT voltage (Complement To Absolute Temperature). The output voltage

varies inversely with device temperature with an absolute accuracy of better than ±5

C

over the full temperature range (

40 C to +105 C). The temperature sensor is only

approximately linear with a slight curvature. The output voltage is measured over different

ranges of temperatures and fit with linear-least-square lines.

After power-up, the temperature sensor output must be allowed to settle to its stable value

before it can be used as an accurate ADC input.

For an accurate measurement of the temperature sensor by the ADC, the ADC must be

configured in single-channel burst mode. The last value of a nine-conversion (or more)

burst provides an accurate result.

8.28 Internal voltage reference

The internal voltage reference is an accurate 0.9 V and is the output of a low voltage band

gap circuit. A typical value at Tamb = 25 C is 0.905 V. The internal voltage reference can

be used in the following applications:

• When the supply voltage VDD is known accurately, the internal voltage reference can

be used to reduce the offset error EO of the ADC code output. The ADC error

correction then increases the accuracy of temperature sensor voltage output

measurements.

LPC1547JBD48 Datasheet(PDF) 41 Page - NXP Semiconductors

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